1. Field of the Invention
This invention relates to computing systems and more particularly to the boot ROM associated therewith.
2. Description of the Related Art
Computing systems typically include a set of built-in software routines that execute at power up as part of “booting the system” and occur each time the system powers up or is reset. These routines are commonly coded in assembly language, and stored in a nonvolatile memory such as a Read Only Memory (ROM) or a Programmable ROM (PROM) such as an Erasable PROM (EPROM), or an Electrically Erasable PROM (EEPROM). Storage in nonvolatile memory ensures that these routines will always be available, including for booting the system, and will not be damaged by disk failures. However, because Random Access Memory (RAM) is faster than ROM, these routines may be copied from ROM to RAM each time the computer is booted. Many modern computers store these routines in a flash memory, which allows updating these routines, if necessary.
In some computer systems (e.g., Personal Computer Advanced Technology (PC-AT) computers), these routines are included in software referred to as the basic input/output system (BIOS). The BIOS performs various functions, including inventorying, testing, and initializing system components. The BIOS facilitates programmer and user interaction with the system hardware. The operating system and application programs of a computer system can access the BIOS rather than directly manipulating I/O ports, registers and control words of the specific system hardware. The BIOS can be accessed through an interface of software interrupts and contains a plurality of entry points respectively corresponding to the different interrupts.
Computer systems often include expansion printed circuit boards (PCBs) for increasing the capabilities of the system and for connecting to peripheral devices. For example, various multimedia devices are commonly implemented as add-in cards or as integrated circuits for installation on a system board. BIOS extensions, also called ROM extensions, are BIOS routines on an option card that are detected by the system BIOS upon bootup. Typically, the BIOS extensions are provided to the system by a separate ROM, often called an option ROM, with a separate address range.
Referring to FIG. 1, a prior art computer system 100 includes CPU 102 connected to I/O hub 104. The I/O hub 104 may be a Southbridge circuit or other appropriate interface module. Low Pin Count (LPC) Bus 110 connects I/O hub 104 to a BIOS ROM 106 that stores a nonvolatile version of BIOS code. The I/O hub 104 provides the interface between the CPU and Peripheral Component Interconnect (PCI) Bus 112 that connects option ROM 108 to the I/O hub. Upon powering up the system, CPU 102 loads the system BIOS from BIOS ROM 106. During bootup, the system BIOS searches for option cards on PCI Bus 112. The BIOS identifies option ROM 108, and assigns addresses to this ROM extension.
Computer systems that give multiple clients access to the same data or resources are called servers. A server farm is a group of networked servers that reside in a single location. Processes are distributed among these servers to improve performance and reliability of processes running on the individual servers. Each server contains a BIOS ROM and can include multiple option cards. Occasionally, the BIOS and option ROM routines require debug, patches, or updates. After the original BIOS code is deployed in a system, it can be costly and inefficient to locally debug, patch, or update the BIOS ROMs and BIOS extensions in each server. Thus, it would be desirable to provide a simplified mechanism for debugging, updating, and patching the system BIOS and BIOS extensions while reducing the number of system components.